1. Field
The present disclosure relates to an apparatus and method for controlling operation of inverter system, and more particularly to an apparatus for controlling operation of inverter system configured to drive a motor by using an inverter, and to normally operate the motor in a resonance-generated frequency band if the resonance occurs, and a method thereof.
2. Background
In general, a mechanical resonance frequency exists in a motor that is generated from the motor itself. An inverter system accurately driving the motor and parts such as transformers mounted on the inverter system also have intrinsic electrical resonance frequency.
In a case a motor is driven by an inverter system including a general inverter and a cascade H-bridge type high voltage inverter, a new resonance frequency caused by mutual influences among the parts as well as intrinsic resonance frequency of each part are generated.
In a case the motor is driven by the inverter system in the abovementioned resonance frequency, the inverter system is not normally operated due to over-current. Furthermore, the motor may be damaged by the over-current, and in worst case, a rotation shaft of the motor may be twisted or broken.
Although many efforts are being waged to remove the resonance frequency in manufacturing/designing an inverter system in consideration of durability and mechanical combination, there is no way of completely removing the resonance frequency.
Therefore, as a way of avoiding an operation in the resonance frequency in the conventional inverter system, the motor is made not to normally operate in a frequency band in which the resonance frequency is generated, but to pass the frequency band the resonance frequency is generated in.
That is, the conventional system of avoiding the resonance frequency used a frequency jump method. In the frequency jump method, a resonance frequency band, i.e., a lowermost frequency and an uppermost frequency, is detected in which a current hunting is generated while the motor is driven where the inverter system is under no load, and then, a target frequency where the inverter system drives the motor is made not to be set up between the lowermost and the uppermost frequency.
However, the frequency jump method has disadvantageous in that it is so made as not to set up the target frequency at the resonance frequency band, such that it is very difficult to prevent the motor from passing the resonance frequency band and to avoid the current hunting. Another disadvantage in the frequency jump method is that it is not to remove the resonance frequency band but to avoid the same, such that an acceleration time of the motor is lengthened, and the over-current hunting is continued if the motor is operated in the resonance frequency band.